Help!!!

[Veeran333]

I have a 120 gallon tank with 6 discus (4 to 5 inches) and 24 cardinal tetras. 83F. 0 ammonia, 0 Nitrite and 20ppm nitrate. I had them for almost a month now. In the beginning they all use to come up to me during feeding time and were very active. But for the past week they don't come up to me, even when I feed and they just hang in the back. One of them is turning a bit dark (it was blue). Very scared, please help.

[Phillydubs]

You should head to the disease section and fill out the questions, it will allow all the folks here to help you more.

How often do you change water? Have you added any new tankmates...

Your nitrates are higher people always say around 5 even 10 is so so but 20 is high, why is that?

I would start with a big water change and try and keep up with big changes to help them.

[jmf3460]

I agree with Phil OP, your nitrates are high which may be causing stress to your fish causing them to feel insecure and hide in the back.